function plot_function_2d(left, right, bottom, top, Nx, Ny, function_f)

node = process_node_elem_2d(left, right, bottom, top, Nx, Ny, "P1");

X = reshape(node(:,1), Ny+1, Nx+1);
Y = reshape(node(:,2), Ny+1, Nx+1);
surf(X, Y, function_f(X, Y));

end